This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Medical devices such as those used for monitoring a patient's vital sign or other physiologic variable, are commonly comprised of a patient-contacting signal transducer and a monitor that connects to the transducer, processes the signals, and provides information to the caregiver. Typically, the transducer is connected to the monitor with and interface cable that includes wires for conducting electrical signals.
An ideal cable and connector assembly for use in such medical devices would be immune to noise interference from external sources as well as crosstalk between wires within the cable and connector assembly. In reality, however, the manufacturing process of a cable and connector assembly includes steps that make the wires within a cable and connector assembly vulnerable to noise, such as capacitive and inductive crosstalk, wherein electrical signals in one wire or pair of wires may interfere or create noise on a nearby wire. The crosstalk may be detrimental to the operation of a medical device. For example, in pulse oximetry, the crosstalk can result in inaccurate readings of SpO2 values.
Cables are generally manufactured to limit the amount of external noise and inductive and capacitive crosstalk that can occur between wires. For example, the cables are bundled together with an electrically insulating protective coating and a conductive shield mesh to protect against environmental noise sources. Additionally, the cables may be made up of twisted wire pairs, commonly referred to as twisted pairs. As their name suggests, the twisted pairs are a pair of wires twisted together in a manner that results in each wire becoming exposed to the same or similar amounts noise elements such that the noise can be nearly or completely canceled out. A twisted pair may be surrounded by an electrically grounded conductive mesh shield to help eliminate noise interference from other wires within the cable bundle. Twisted pairs having the conductive mesh shield are referred to as shielded twisted pairs, while twisted pairs without the conductive mesh are referred to as unshielded twisted pairs. The cables used in medical devices such as pulse oximetry systems are commonly constructed with one or both types of twisted pairs, where multiple sets of wires are combined into a cable bundle. Electrical crosstalk can occur when signal wires electrically contact one another (a “short”), or come into close proximity to adjacent conductors.
In order to connect the wires to connector pins, the cable bundle must be stripped and the wires untwisted. Thus, in this section of the cables, the wires are unprotected and vulnerable to crosstalk interference. Furthermore, after the wires have been connected to connector pins and the pins are placed in a connector housing, even if the wires are initially pushed apart and spatially separated, additional handling and processing may push the wires together and increase the likelihood of crosstalk.